Let's explore why atmospheric pressure decreases with increasing altitude.
1. Definition of Atmospheric Pressure: Atmospheric pressure is the force exerted by the weight of the air above a given point. It is typically measured in kilopascals (kPa) or millibars (mb).
2. Air Density Decreases with Altitude: At higher altitudes, the density of the air decreases. This is because the gravitational pull is weaker further from the Earth's surface, which causes fewer air molecules to be present in a given volume.
3. Weight of the Air Column: Atmospheric pressure at any point is due to the weight of the column of air directly above that point. As altitude increases, the height of this air column decreases, meaning there is less air above that point exerting pressure downwards.
4. Decreasing Mass of Air: Since there are fewer air molecules at higher altitudes, the mass of the air column also decreases. According to the equation for pressure (Pressure = Force/Area), with a decreasing mass of air, both the gravitational force (weight) and the resultant pressure decrease.
5. Impact of Gravity: Gravity's effect on air reduces with altitude. Objects, including air molecules, experience slightly less gravitational pull as they move further from the Earth’s center. This slightly reduced gravitational force allows air molecules to be less densely packed.
6. Temperature Changes: Temperature often decreases with altitude (environmental lapse rate), which impacts the pressure as colder air is denser at lower altitudes but thins out when moved to higher altitudes.
By these cumulative points, as altitude increases, atmospheric pressure naturally decreases due to the reduced density, lesser weight of the air column, and varying gravitational impact. Hence, the higher you go, the lower the atmospheric pressure you will experience.
